name-hash.c

   1 /*
   2  * name-hash.c
   3  *
   4  * Hashing names in the index state
   5  *
   6  * Copyright (C) 2008 Linus Torvalds
   7  */
   8 #define NO_THE_INDEX_COMPATIBILITY_MACROS
   9 #include "cache.h"
  10
  11 struct dir_entry {
  12         struct hashmap_entry ent;
  13         struct dir_entry *parent;
  14         int nr;
  15         unsigned int namelen;
  16         char name[FLEX_ARRAY];
  17 };
  18
  19 static int dir_entry_cmp(const struct dir_entry *e1,
  20                 const struct dir_entry *e2, const char *name)
  21 {
  22         return e1->namelen != e2->namelen || strncasecmp(e1->name,
  23                         name ? name : e2->name, e1->namelen);
  24 }
  25
  26 static struct dir_entry *find_dir_entry__hash(struct index_state *istate,
  27                 const char *name, unsigned int namelen, unsigned int hash)
  28 {
  29         struct dir_entry key;
  30         hashmap_entry_init(&key, hash);
  31         key.namelen = namelen;
  32         return hashmap_get(&istate->dir_hash, &key, name);
  33 }
  34
  35 static struct dir_entry *find_dir_entry(struct index_state *istate,
  36                 const char *name, unsigned int namelen)
  37 {
  38         return find_dir_entry__hash(istate, name, namelen, memihash(name, namelen));
  39 }
  40
  41 static struct dir_entry *hash_dir_entry(struct index_state *istate,
  42                 struct cache_entry *ce, int namelen)
  43 {
  44         /*
  45          * Throw each directory component in the hash for quick lookup
  46          * during a git status. Directory components are stored without their
  47          * closing slash.  Despite submodules being a directory, they never
  48          * reach this point, because they are stored
  49          * in index_state.name_hash (as ordinary cache_entries).
  50          */
  51         struct dir_entry *dir;
  52
  53         /* get length of parent directory */
  54         while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
  55                 namelen--;
  56         if (namelen <= 0)
  57                 return NULL;
  58         namelen--;
  59
  60         /* lookup existing entry for that directory */
  61         dir = find_dir_entry(istate, ce->name, namelen);
  62         if (!dir) {
  63                 /* not found, create it and add to hash table */
  64                 FLEX_ALLOC_MEM(dir, name, ce->name, namelen);
  65                 hashmap_entry_init(dir, memihash(ce->name, namelen));
  66                 dir->namelen = namelen;
  67                 hashmap_add(&istate->dir_hash, dir);
  68
  69                 /* recursively add missing parent directories */
  70                 dir->parent = hash_dir_entry(istate, ce, namelen);
  71         }
  72         return dir;
  73 }
  74
  75 static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
  76 {
  77         /* Add reference to the directory entry (and parents if 0). */
  78         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  79         while (dir && !(dir->nr++))
  80                 dir = dir->parent;
  81 }
  82
  83 static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
  84 {
  85         /*
  86          * Release reference to the directory entry. If 0, remove and continue
  87          * with parent directory.
  88          */
  89         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  90         while (dir && !(--dir->nr)) {
  91                 struct dir_entry *parent = dir->parent;
  92                 hashmap_remove(&istate->dir_hash, dir, NULL);
  93                 free(dir);
  94                 dir = parent;
  95         }
  96 }
  97
  98 static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
  99 {
 100         if (ce->ce_flags & CE_HASHED)
 101                 return;
 102         ce->ce_flags |= CE_HASHED;
 103         hashmap_entry_init(ce, memihash(ce->name, ce_namelen(ce)));
 104         hashmap_add(&istate->name_hash, ce);
 105
 106         if (ignore_case)
 107                 add_dir_entry(istate, ce);
 108 }
 109
 110 static int cache_entry_cmp(const struct cache_entry *ce1,
 111                 const struct cache_entry *ce2, const void *remove)
 112 {
 113         /*
 114          * For remove_name_hash, find the exact entry (pointer equality); for
 115          * index_file_exists, find all entries with matching hash code and
 116          * decide whether the entry matches in same_name.
 117          */
 118         return remove ? !(ce1 == ce2) : 0;
 119 }
 120
 121 static int lazy_try_threaded = 1;
 122 static int lazy_nr_dir_threads;
 123
 124 #ifdef NO_PTHREADS
 125
 126 static inline int lookup_lazy_params(struct index_state *istate)
 127 {
 128         return 0;
 129 }
 130
 131 static inline void threaded_lazy_init_name_hash(
 132         struct index_state *istate)
 133 {
 134 }
 135
 136 #else
 137
 138 #include "thread-utils.h"
 139
 140 /*
 141  * Set a minimum number of cache_entries that we will handle per
 142  * thread and use that to decide how many threads to run (upto
 143  * the number on the system).
 144  *
 145  * For guidance setting the lower per-thread bound, see:
 146  *     t/helper/test-lazy-init-name-hash --analyze
 147  */
 148 #define LAZY_THREAD_COST (2000)
 149
 150 /*
 151  * We use n mutexes to guard n partitions of the "istate->dir_hash"
 152  * hashtable.  Since "find" and "insert" operations will hash to a
 153  * particular bucket and modify/search a single chain, we can say
 154  * that "all chains mod n" are guarded by the same mutex -- rather
 155  * than having a single mutex to guard the entire table.  (This does
 156  * require that we disable "rehashing" on the hashtable.)
 157  *
 158  * So, a larger value here decreases the probability of a collision
 159  * and the time that each thread must wait for the mutex.
 160  */
 161 #define LAZY_MAX_MUTEX   (32)
 162
 163 static pthread_mutex_t *lazy_dir_mutex_array;
 164
 165 /*
 166  * An array of lazy_entry items is used by the n threads in
 167  * the directory parse (first) phase to (lock-free) store the
 168  * intermediate results.  These values are then referenced by
 169  * the 2 threads in the second phase.
 170  */
 171 struct lazy_entry {
 172         struct dir_entry *dir;
 173         unsigned int hash_dir;
 174         unsigned int hash_name;
 175 };
 176
 177 /*
 178  * Decide if we want to use threads (if available) to load
 179  * the hash tables.  We set "lazy_nr_dir_threads" to zero when
 180  * it is not worth it.
 181  */
 182 static int lookup_lazy_params(struct index_state *istate)
 183 {
 184         int nr_cpus;
 185
 186         lazy_nr_dir_threads = 0;
 187
 188         if (!lazy_try_threaded)
 189                 return 0;
 190
 191         /*
 192          * If we are respecting case, just use the original
 193          * code to build the "istate->name_hash".  We don't
 194          * need the complexity here.
 195          */
 196         if (!ignore_case)
 197                 return 0;
 198
 199         nr_cpus = online_cpus();
 200         if (nr_cpus < 2)
 201                 return 0;
 202
 203         if (istate->cache_nr < 2 * LAZY_THREAD_COST)
 204                 return 0;
 205
 206         if (istate->cache_nr < nr_cpus * LAZY_THREAD_COST)
 207                 nr_cpus = istate->cache_nr / LAZY_THREAD_COST;
 208         lazy_nr_dir_threads = nr_cpus;
 209         return lazy_nr_dir_threads;
 210 }
 211
 212 /*
 213  * Initialize n mutexes for use when searching and inserting
 214  * into "istate->dir_hash".  All "dir" threads are trying
 215  * to insert partial pathnames into the hash as they iterate
 216  * over their portions of the index, so lock contention is
 217  * high.
 218  *
 219  * However, the hashmap is going to put items into bucket
 220  * chains based on their hash values.  Use that to create n
 221  * mutexes and lock on mutex[bucket(hash) % n].  This will
 222  * decrease the collision rate by (hopefully) by a factor of n.
 223  */
 224 static void init_dir_mutex(void)
 225 {
 226         int j;
 227
 228         lazy_dir_mutex_array = xcalloc(LAZY_MAX_MUTEX, sizeof(pthread_mutex_t));
 229
 230         for (j = 0; j < LAZY_MAX_MUTEX; j++)
 231                 init_recursive_mutex(&lazy_dir_mutex_array[j]);
 232 }
 233
 234 static void cleanup_dir_mutex(void)
 235 {
 236         int j;
 237
 238         for (j = 0; j < LAZY_MAX_MUTEX; j++)
 239                 pthread_mutex_destroy(&lazy_dir_mutex_array[j]);
 240
 241         free(lazy_dir_mutex_array);
 242 }
 243
 244 static void lock_dir_mutex(int j)
 245 {
 246         pthread_mutex_lock(&lazy_dir_mutex_array[j]);
 247 }
 248
 249 static void unlock_dir_mutex(int j)
 250 {
 251         pthread_mutex_unlock(&lazy_dir_mutex_array[j]);
 252 }
 253
 254 static inline int compute_dir_lock_nr(
 255         const struct hashmap *map,
 256         unsigned int hash)
 257 {
 258         return hashmap_bucket(map, hash) % LAZY_MAX_MUTEX;
 259 }
 260
 261 static struct dir_entry *hash_dir_entry_with_parent_and_prefix(
 262         struct index_state *istate,
 263         struct dir_entry *parent,
 264         struct strbuf *prefix)
 265 {
 266         struct dir_entry *dir;
 267         unsigned int hash;
 268         int lock_nr;
 269
 270         /*
 271          * Either we have a parent directory and path with slash(es)
 272          * or the directory is an immediate child of the root directory.
 273          */
 274         assert((parent != NULL) ^ (strchr(prefix->buf, '/') == NULL));
 275
 276         if (parent)
 277                 hash = memihash_cont(parent->ent.hash,
 278                         prefix->buf + parent->namelen,
 279                         prefix->len - parent->namelen);
 280         else
 281                 hash = memihash(prefix->buf, prefix->len);
 282
 283         lock_nr = compute_dir_lock_nr(&istate->dir_hash, hash);
 284         lock_dir_mutex(lock_nr);
 285
 286         dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash);
 287         if (!dir) {
 288                 FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len);
 289                 hashmap_entry_init(dir, hash);
 290                 dir->namelen = prefix->len;
 291                 dir->parent = parent;
 292                 hashmap_add(&istate->dir_hash, dir);
 293
 294                 if (parent) {
 295                         unlock_dir_mutex(lock_nr);
 296
 297                         /* All I really need here is an InterlockedIncrement(&(parent->nr)) */
 298                         lock_nr = compute_dir_lock_nr(&istate->dir_hash, parent->ent.hash);
 299                         lock_dir_mutex(lock_nr);
 300                         parent->nr++;
 301                 }
 302         }
 303
 304         unlock_dir_mutex(lock_nr);
 305
 306         return dir;
 307 }
 308
 309 /*
 310  * handle_range_1() and handle_range_dir() are derived from
 311  * clear_ce_flags_1() and clear_ce_flags_dir() in unpack-trees.c
 312  * and handle the iteration over the entire array of index entries.
 313  * They use recursion for adjacent entries in the same parent
 314  * directory.
 315  */
 316 static int handle_range_1(
 317         struct index_state *istate,
 318         int k_start,
 319         int k_end,
 320         struct dir_entry *parent,
 321         struct strbuf *prefix,
 322         struct lazy_entry *lazy_entries);
 323
 324 static int handle_range_dir(
 325         struct index_state *istate,
 326         int k_start,
 327         int k_end,
 328         struct dir_entry *parent,
 329         struct strbuf *prefix,
 330         struct lazy_entry *lazy_entries,
 331         struct dir_entry **dir_new_out)
 332 {
 333         int rc, k;
 334         int input_prefix_len = prefix->len;
 335         struct dir_entry *dir_new;
 336
 337         dir_new = hash_dir_entry_with_parent_and_prefix(istate, parent, prefix);
 338
 339         strbuf_addch(prefix, '/');
 340
 341         /*
 342          * Scan forward in the index array for index entries having the same
 343          * path prefix (that are also in this directory).
 344          */
 345         if (k_start + 1 >= k_end)
 346                 k = k_end;
 347         else if (strncmp(istate->cache[k_start + 1]->name, prefix->buf, prefix->len) > 0)
 348                 k = k_start + 1;
 349         else if (strncmp(istate->cache[k_end - 1]->name, prefix->buf, prefix->len) == 0)
 350                 k = k_end;
 351         else {
 352                 int begin = k_start;
 353                 int end = k_end;
 354                 while (begin < end) {
 355                         int mid = (begin + end) >> 1;
 356                         int cmp = strncmp(istate->cache[mid]->name, prefix->buf, prefix->len);
 357                         if (cmp == 0) /* mid has same prefix; look in second part */
 358                                 begin = mid + 1;
 359                         else if (cmp > 0) /* mid is past group; look in first part */
 360                                 end = mid;
 361                         else
 362                                 die("cache entry out of order");
 363                 }
 364                 k = begin;
 365         }
 366
 367         /*
 368          * Recurse and process what we can of this subset [k_start, k).
 369          */
 370         rc = handle_range_1(istate, k_start, k, dir_new, prefix, lazy_entries);
 371
 372         strbuf_setlen(prefix, input_prefix_len);
 373
 374         *dir_new_out = dir_new;
 375         return rc;
 376 }
 377
 378 static int handle_range_1(
 379         struct index_state *istate,
 380         int k_start,
 381         int k_end,
 382         struct dir_entry *parent,
 383         struct strbuf *prefix,
 384         struct lazy_entry *lazy_entries)
 385 {
 386         int input_prefix_len = prefix->len;
 387         int k = k_start;
 388
 389         while (k < k_end) {
 390                 struct cache_entry *ce_k = istate->cache[k];
 391                 const char *name, *slash;
 392
 393                 if (prefix->len && strncmp(ce_k->name, prefix->buf, prefix->len))
 394                         break;
 395
 396                 name = ce_k->name + prefix->len;
 397                 slash = strchr(name, '/');
 398
 399                 if (slash) {
 400                         int len = slash - name;
 401                         int processed;
 402                         struct dir_entry *dir_new;
 403
 404                         strbuf_add(prefix, name, len);
 405                         processed = handle_range_dir(istate, k, k_end, parent, prefix, lazy_entries, &dir_new);
 406                         if (processed) {
 407                                 k += processed;
 408                                 strbuf_setlen(prefix, input_prefix_len);
 409                                 continue;
 410                         }
 411
 412                         strbuf_addch(prefix, '/');
 413                         processed = handle_range_1(istate, k, k_end, dir_new, prefix, lazy_entries);
 414                         k += processed;
 415                         strbuf_setlen(prefix, input_prefix_len);
 416                         continue;
 417                 }
 418
 419                 /*
 420                  * It is too expensive to take a lock to insert "ce_k"
 421                  * into "istate->name_hash" and increment the ref-count
 422                  * on the "parent" dir.  So we defer actually updating
 423                  * permanent data structures until phase 2 (where we
 424                  * can change the locking requirements) and simply
 425                  * accumulate our current results into the lazy_entries
 426                  * data array).
 427                  *
 428                  * We do not need to lock the lazy_entries array because
 429                  * we have exclusive access to the cells in the range
 430                  * [k_start,k_end) that this thread was given.
 431                  */
 432                 lazy_entries[k].dir = parent;
 433                 if (parent) {
 434                         lazy_entries[k].hash_name = memihash_cont(
 435                                 parent->ent.hash,
 436                                 ce_k->name + parent->namelen,
 437                                 ce_namelen(ce_k) - parent->namelen);
 438                         lazy_entries[k].hash_dir = parent->ent.hash;
 439                 } else {
 440                         lazy_entries[k].hash_name = memihash(ce_k->name, ce_namelen(ce_k));
 441                 }
 442
 443                 k++;
 444         }
 445
 446         return k - k_start;
 447 }
 448
 449 struct lazy_dir_thread_data {
 450         pthread_t pthread;
 451         struct index_state *istate;
 452         struct lazy_entry *lazy_entries;
 453         int k_start;
 454         int k_end;
 455 };
 456
 457 static void *lazy_dir_thread_proc(void *_data)
 458 {
 459         struct lazy_dir_thread_data *d = _data;
 460         struct strbuf prefix = STRBUF_INIT;
 461         handle_range_1(d->istate, d->k_start, d->k_end, NULL, &prefix, d->lazy_entries);
 462         strbuf_release(&prefix);
 463         return NULL;
 464 }
 465
 466 struct lazy_name_thread_data {
 467         pthread_t pthread;
 468         struct index_state *istate;
 469         struct lazy_entry *lazy_entries;
 470 };
 471
 472 static void *lazy_name_thread_proc(void *_data)
 473 {
 474         struct lazy_name_thread_data *d = _data;
 475         int k;
 476
 477         for (k = 0; k < d->istate->cache_nr; k++) {
 478                 struct cache_entry *ce_k = d->istate->cache[k];
 479                 ce_k->ce_flags |= CE_HASHED;
 480                 hashmap_entry_init(ce_k, d->lazy_entries[k].hash_name);
 481                 hashmap_add(&d->istate->name_hash, ce_k);
 482         }
 483
 484         return NULL;
 485 }
 486
 487 static inline void lazy_update_dir_ref_counts(
 488         struct index_state *istate,
 489         struct lazy_entry *lazy_entries)
 490 {
 491         int k;
 492
 493         for (k = 0; k < istate->cache_nr; k++) {
 494                 if (lazy_entries[k].dir)
 495                         lazy_entries[k].dir->nr++;
 496         }
 497 }
 498
 499 static void threaded_lazy_init_name_hash(
 500         struct index_state *istate)
 501 {
 502         int nr_each;
 503         int k_start;
 504         int t;
 505         struct lazy_entry *lazy_entries;
 506         struct lazy_dir_thread_data *td_dir;
 507         struct lazy_name_thread_data *td_name;
 508
 509         k_start = 0;
 510         nr_each = DIV_ROUND_UP(istate->cache_nr, lazy_nr_dir_threads);
 511
 512         lazy_entries = xcalloc(istate->cache_nr, sizeof(struct lazy_entry));
 513         td_dir = xcalloc(lazy_nr_dir_threads, sizeof(struct lazy_dir_thread_data));
 514         td_name = xcalloc(1, sizeof(struct lazy_name_thread_data));
 515
 516         init_dir_mutex();
 517
 518         /*
 519          * Phase 1:
 520          * Build "istate->dir_hash" using n "dir" threads (and a read-only index).
 521          */
 522         for (t = 0; t < lazy_nr_dir_threads; t++) {
 523                 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
 524                 td_dir_t->istate = istate;
 525                 td_dir_t->lazy_entries = lazy_entries;
 526                 td_dir_t->k_start = k_start;
 527                 k_start += nr_each;
 528                 if (k_start > istate->cache_nr)
 529                         k_start = istate->cache_nr;
 530                 td_dir_t->k_end = k_start;
 531                 if (pthread_create(&td_dir_t->pthread, NULL, lazy_dir_thread_proc, td_dir_t))
 532                         die("unable to create lazy_dir_thread");
 533         }
 534         for (t = 0; t < lazy_nr_dir_threads; t++) {
 535                 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
 536                 if (pthread_join(td_dir_t->pthread, NULL))
 537                         die("unable to join lazy_dir_thread");
 538         }
 539
 540         /*
 541          * Phase 2:
 542          * Iterate over all index entries and add them to the "istate->name_hash"
 543          * using a single "name" background thread.
 544          * (Testing showed it wasn't worth running more than 1 thread for this.)
 545          *
 546          * Meanwhile, finish updating the parent directory ref-counts for each
 547          * index entry using the current thread.  (This step is very fast and
 548          * doesn't need threading.)
 549          */
 550         td_name->istate = istate;
 551         td_name->lazy_entries = lazy_entries;
 552         if (pthread_create(&td_name->pthread, NULL, lazy_name_thread_proc, td_name))
 553                 die("unable to create lazy_name_thread");
 554
 555         lazy_update_dir_ref_counts(istate, lazy_entries);
 556
 557         if (pthread_join(td_name->pthread, NULL))
 558                 die("unable to join lazy_name_thread");
 559
 560         cleanup_dir_mutex();
 561
 562         free(td_name);
 563         free(td_dir);
 564         free(lazy_entries);
 565 }
 566
 567 #endif
 568
 569 static void lazy_init_name_hash(struct index_state *istate)
 570 {
 571         if (istate->name_hash_initialized)
 572                 return;
 573         hashmap_init(&istate->name_hash, (hashmap_cmp_fn) cache_entry_cmp,
 574                         istate->cache_nr);
 575         hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp,
 576                         istate->cache_nr);
 577
 578         if (lookup_lazy_params(istate)) {
 579                 hashmap_disallow_rehash(&istate->dir_hash, 1);
 580                 threaded_lazy_init_name_hash(istate);
 581                 hashmap_disallow_rehash(&istate->dir_hash, 0);
 582         } else {
 583                 int nr;
 584                 for (nr = 0; nr < istate->cache_nr; nr++)
 585                         hash_index_entry(istate, istate->cache[nr]);
 586         }
 587
 588         istate->name_hash_initialized = 1;
 589 }
 590
 591 /*
 592  * A test routine for t/helper/ sources.
 593  *
 594  * Returns the number of threads used or 0 when
 595  * the non-threaded code path was used.
 596  *
 597  * Requesting threading WILL NOT override guards
 598  * in lookup_lazy_params().
 599  */
 600 int test_lazy_init_name_hash(struct index_state *istate, int try_threaded)
 601 {
 602         lazy_nr_dir_threads = 0;
 603         lazy_try_threaded = try_threaded;
 604
 605         lazy_init_name_hash(istate);
 606
 607         return lazy_nr_dir_threads;
 608 }
 609
 610 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 611 {
 612         if (istate->name_hash_initialized)
 613                 hash_index_entry(istate, ce);
 614 }
 615
 616 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 617 {
 618         if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))
 619                 return;
 620         ce->ce_flags &= ~CE_HASHED;
 621         hashmap_remove(&istate->name_hash, ce, ce);
 622
 623         if (ignore_case)
 624                 remove_dir_entry(istate, ce);
 625 }
 626
 627 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
 628 {
 629         if (len1 != len2)
 630                 return 0;
 631
 632         while (len1) {
 633                 unsigned char c1 = *name1++;
 634                 unsigned char c2 = *name2++;
 635                 len1--;
 636                 if (c1 != c2) {
 637                         c1 = toupper(c1);
 638                         c2 = toupper(c2);
 639                         if (c1 != c2)
 640                                 return 0;
 641                 }
 642         }
 643         return 1;
 644 }
 645
 646 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
 647 {
 648         int len = ce_namelen(ce);
 649
 650         /*
 651          * Always do exact compare, even if we want a case-ignoring comparison;
 652          * we do the quick exact one first, because it will be the common case.
 653          */
 654         if (len == namelen && !memcmp(name, ce->name, len))
 655                 return 1;
 656
 657         if (!icase)
 658                 return 0;
 659
 660         return slow_same_name(name, namelen, ce->name, len);
 661 }
 662
 663 int index_dir_exists(struct index_state *istate, const char *name, int namelen)
 664 {
 665         struct dir_entry *dir;
 666
 667         lazy_init_name_hash(istate);
 668         dir = find_dir_entry(istate, name, namelen);
 669         return dir && dir->nr;
 670 }
 671
 672 void adjust_dirname_case(struct index_state *istate, char *name)
 673 {
 674         const char *startPtr = name;
 675         const char *ptr = startPtr;
 676
 677         lazy_init_name_hash(istate);
 678         while (*ptr) {
 679                 while (*ptr && *ptr != '/')
 680                         ptr++;
 681
 682                 if (*ptr == '/') {
 683                         struct dir_entry *dir;
 684
 685                         ptr++;
 686                         dir = find_dir_entry(istate, name, ptr - name + 1);
 687                         if (dir) {
 688                                 memcpy((void *)startPtr, dir->name + (startPtr - name), ptr - startPtr);
 689                                 startPtr = ptr;
 690                         }
 691                 }
 692         }
 693 }
 694
 695 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 696 {
 697         struct cache_entry *ce;
 698
 699         lazy_init_name_hash(istate);
 700
 701         ce = hashmap_get_from_hash(&istate->name_hash,
 702                                    memihash(name, namelen), NULL);
 703         while (ce) {
 704                 if (same_name(ce, name, namelen, icase))
 705                         return ce;
 706                 ce = hashmap_get_next(&istate->name_hash, ce);
 707         }
 708         return NULL;
 709 }
 710
 711 void free_name_hash(struct index_state *istate)
 712 {
 713         if (!istate->name_hash_initialized)
 714                 return;
 715         istate->name_hash_initialized = 0;
 716
 717         hashmap_free(&istate->name_hash, 0);
 718         hashmap_free(&istate->dir_hash, 1);
 719 }